In the industry involving high speed automated handling of printed circuit boards, the boards typically are moved from station to station for step-wise performance of functions such as mounting components on opposite sides of the board, testing the components, soldering, and the like. It is therefore often necessary after operating on an upper surface of the boards at one station to flip the boards so as to operate on the lower surface thereof at the next station. Numerous devices for inverting printed circuit boards travelling along a conveyor line to achieve this flipping are known.
U.S. Pat. No. 4,969,552 to Kennicutt et al. discloses a device for flipping circuit boards which includes two U-shaped channels 70 which receive opposite edges of the board. The outer peripheries of feed wheels 60, which are driven by motor 50 via belt 56, protrude into channels 70 to engage and drive the board into and out of the flipping device. The complex flipping operation involves lifting one end of channels 70 and flipping it end-over-end, while at the same moving the opposite end of channels 70 in a horizontal plane toward the original position of the first end.
The device disclosed in Kennicut et al, however, has a number of disadvantages. As printed circuit board technology advances and the size of the boards themselves and the components mounted thereon decreases, the printed circuit boards are becoming more and more fragile. Inverters such as those disclosed in Kennicutt et al., which lift the boards completely off of the drive rollers, can easily damage the fragile boards. Another problem associated with the decreasing size of printed circuit boards and associated components is that more precise placement of the boards along the conveyor lines is necessary for proper manipulation of the board faces. The Kennicutt et al. device which lifts the boards off the assembly line during inversion thereof may not meet the demanding precision requirements.
U.S. Pat. No. 5,297,568 to Schmid discloses a device for treatment of printed circuit boards which includes a turning over mechanism 16. Mechanism 16 includes a conveying means 32 which comprises two endless belts 34, 35 which are drivable in opposite directions to secure the circuit boards 23 therebetween. During operation, conveying means 32 moves board 23 horizontally until the entire board 23 is within mechanism 16, at which point mechanism 16 rotates conveying means 32 and board 23 about a horizontal axis 46a, b, c. Conveying means 32 then causes board 23 to exit the opposite end of mechanism 16.
Although Schmid does not suffer from the disadvantages discussed above, the device disclosed in Schmid suffers from its own disadvantages. Schmid discloses two endless belts, one above and one below the board, drivable in opposite directions for securing the board therebetween. However, nothing is disclosed as to how the two belts are driven. The drive of the belts is critical because if the speed of the two belts is not substantially identical, the boards may become misaligned, thereby possibly causing damage to the board, jamming of the conveyor, or failure to maintain precise tolerances along the assembly line. Schmid does not disclose any means to maintain the necessary precise timing of the belts.
Furthermore, neither of the prior art patents discussed above discloses an inverter which can be used in a conveyor system having two side-by-side driven lanes. Such a dual lane conveyor system is desirable to increase production and efficiency of the assembly line by effectively doubling the number of printed circuit boards which can be processed in any given time period. However, a major concern of dual lane conveyor systems is the space required for such systems, particularly when a single lane conveyor, or a portion thereof, is being replaced by a dual lane conveyor system. For example, to minimize the width of the conveyor system as a whole, and the inverter in particular, it is desirable to have a space of less than approximately two inches between the two lanes. Neither of the prior art patents discussed above recognizes that the width of a flipping device is critical, and thus neither is concerned with minimizing the width of the device. As such, neither of the patents discloses a device which can meet the demanding width requirements of a dual lane conveyor system.
What is desired, therefore, is an inverter for use in a conveyor system which has two side-by-side driven lanes, which minimizes the chance of damage to the articles being flipped, which maintains precise placement of the articles, which maintains the necessary precise timing of the drive belts, which has a relatively small overall width, and which allows for a distance between the lanes of less than approximately two inches.